Understanding pain can be difficult due to a plethora of different types of terminology, different nomenclature, and oftentimes even overlapping and contradictory criteria for diagnosis. This chapter intends to clarify and consolidate varied nomenclature and provides a foundation to communicate and advance the understanding of pain medicine. Basic definitions of common pain syndromes and treatments are included and will be expounded upon in this text.
Keywordschronic pain, pain medicine, pain syndromes, spine, taxonomy
Acute pain —Pain resulting from nociceptor activation due to damage or potential damage to tissues. Acute pain typically resolves after the tissue damage is repaired.
Allodynia —Pain due to a stimulus that does not normally provoke pain.
Analgesia —Absence of pain in response to stimulation that would normally be painful.
Anesthesia —Absence of all sensory modalities.
Anesthesia dolorosa —Pain in an area or region that is anesthetic.
Budapest criteria —An empirically driven and statistically derived criteria developed to objectively diagnose complex regional pain syndrome (CRPS) using the patient’s history and physical examination findings.
Carpal tunnel syndrome —Pain in the hand, usually occurring at night, due to entrapment of the median nerve in the carpal tunnel area. The quality of the pain is a “pins-and-needles” sensation, stinging, burning, or aching. There may be decreased sensation on the tips of the first to third fingers, positive Tinel sign, and, rarely, atrophy of the thenar muscles. A nerve conduction study shows delayed conduction across the carpal tunnel. The syndrome is caused by compression of the median nerve in the wrist between the carpal bones and the flexor retinaculum (transverse carpal ligament).
Central pain —Pain caused by a lesion or disease of the central somatosensory nervous system. Central pain is usually associated with abnormal sensibility to temperature and to noxious stimulation.
Chronic pain —Pain that persists beyond the course of an acute disease or a reasonable time for an injury to heal or that is associated with a chronic pathologic process that causes continuous pain or the pain recurs at intervals of months or years. Some investigators use duration of ≥6 months to designate pain as chronic.
Claudication pain —Crampy, achy lower extremity pain precipitated by ambulation and activity, caused by vascular insufficiency. This is to be differentiated from neurogenic claudication, which presents with similar symptoms but due to significant central spinal canal stenosis.
Complex regional pain syndrome (CRPS; Budapest criteria definition) —An array of painful conditions that are characterized by a continuing (spontaneous and/or evoked) regional pain that is seemingly disproportionate in time or degree to the usual course of any known trauma or other lesion. The pain is regional (not in a specific nerve territory or dermatome) and usually has a distal predominance of abnormal sensory, motor, sudomotor, vasomotor, and/or trophic findings. The syndrome shows variable progression over time. There is an International Association for the Study of Pain (IASP) and Budapest criteria for CRPS ( Tables 3.1 and 3.2 ).
Presence of an initiating noxious event or a cause of immobilization
Continuing pain, allodynia, or hyperalgesia in which the pain is disproportionate to any known inciting event
Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the region of pain (can be sign or symptom)
Diagnosis is excluded by the existence of other conditions that would otherwise account for the degree of pain and dysfunction
CRPS type I: seen without “major nerve damage” diagnose CRPS I
CRPS type II: seen in the presence of “major nerve damage”
To make the clinical diagnosis, the following criteria must be met:
Continuing pain that is disproportionate to any inciting event
Must report at least one symptom in three of the four following categories:
Sensory: Reports of hyperesthesia and/or allodynia
Vasomotor: Reports of temperature asymmetry and/or skin color changes and/or skin color asymmetry
Sudomotor/edema: Reports of edema and/or sweating changes and/or sweating asymmetry
Motor/trophic: Reports of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin)
Must display at least one sign at time of evaluation in two or more of the following categories:
Sensory: Evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch and/or temperature sensation and/or deep somatic pressure and/or joint movement)
Vasomotor: Evidence of temperature asymmetry (>1°C) and/or skin color changes and/or asymmetry
Sudomotor/edema: Evidence of edema and/or sweating changes and/or sweating asymmetry
Motor/trophic: Evidence of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin)
There is no other diagnosis that better explains the signs and symptoms.
For research purposes, diagnostic decision rule should be at least one symptom in all four symptom categories and at least one sign (observed at evaluation) in two or more sign categories.
Comprehensive pain center —Center dedicated to managing a full spectrum of chronic pain syndromes using multiple disciplines and modalities.
Cubital tunnel syndrome —Entrapment of the ulnar nerve in a fibro-osseous tunnel formed by the trochlear groove between the olecranon process and the medial epicondyle of the humerus. A myofascial covering converts the groove to a tunnel, which causes the nerve entrapment. There is pain, numbness, and paresthesia in the distribution of the ulnar nerve and, sometimes, weakness and atrophy in the same distribution. Tinel sign is positive at the elbow. Nerve conduction velocity shows slowing of conduction in the ulnar nerve across the elbow. The intrinsic muscles of the hand may show signs of denervation. Surgery may be required to decompress the entrapment or to transpose the ulnar nerve.
Deafferentation pain —Pain due to loss of sensory input into the central nervous system. This may occur with lesions of peripheral nerves, such as avulsion of the brachial plexus, or due to pathology of the central nervous system.
Disability —Loss of ability to perform a specific task in a standard or normal fashion.
Discogenic pain —Vague, achy low back pain emanating from the disc itself and not attributed to compression of adjacent nerves likely attributable to nociceptor ingrowth into the disc itself. The pain is usually axial in character and worse on standing. Magnetic resonance imaging (MRI) may help in the diagnosis (presence of a “high-intensity zone”) and discography may help to localize the affected vertebral level.
Dysesthesia —An unpleasant abnormal evoked sensation, whether spontaneous or evoked.
Eagle syndrome (stylohyoid syndrome) —Elongated or deviated styloid process and/or calcification of the stylohyoid ligament, which interferes with adjacent anatomical structures giving rise to pain. Pain may be precipitated by trauma to the region.